This invention relates to photographic apparatus and, more particularly, it concerns a camera back construction for retaining a plurality of instant film units for successive exposure and subsequent processing of individual units under conditions assuring that the processing requirements for each film unit are fully met.
In U.S. Pat. No. 4,736,215, issued Apr. 4, 1988, a photographic method and apparatus is disclosed in which one or all film units in a packaging cassette carry machine readable indica by which a variety of camera operating parameters may be adjusted in response to the indicia printed on at least one unit in a given cassette to assure that the unique characteristics of the film units in that cassette are fully accounted for in the resulting camera parameter adjustments. The system represented by the disclosed method and apparatus in that patent is particularly suited to instant film in which the quality of the ultimate photograph is dependent not only on camera exposure parameters, but also on processing variables as the exposed film unit is discharged from the cassette and the camera. Also, the disclosed system is applicable both to integral instant film which, by virtue of its construction, must be mechanically processed and discharged from the camera and to peel-apart instant film which is designed principally for manual withdrawal from the camera retained cassette and through a processing pressure nip for the spread of processing fluid between an exposed negative sheet and a positive sheet of each such film unit on which the resulting photograph is formed.
Although designed for manual removal from the camera during processing, photographs formed with peel-apart instant films are enhanced by automated or motor driven processing of such film units out of the greater degree of predictability in the operation of processing components on the film units as compared with manually pulling the film units in relation to such components. If the benefits of increased predictability of motor driven processors are to be fully realized, however, it is important that the film units and the processor operation be accurately correlated one with the other. For example, the optimum speed at which the film unit is passed through the pressure nip of the processor may vary considerably for different types of peel-apart film constructions. The normal forces acting on the superimposed negative and positive sheets of such a film unit at the processing pressure nip may vary to a degree where it may not be possible to process all types of peel-apart instant film in a given processor with satisfactory results. Also, because the withdrawal of a peel-apart instant film unit from the cassette in which it was packaged and through a processing pressure nip involves a succession of discrete steps, it is important that the various film unit components be properly positioned at the end of each such step of its movement if a motor driven processor is to be reliably effective. Other peel-apart instant film processing adjuncts, such as imbibition timers and the like similarly require adjustment to account for sensitometry and chemical variances of diverse film unit types. For these reasons and others, the system disclosed in the afore-mentioned patent, in which machine readable indicia is provided on each film unit, is particularly applicable to the provision of a motor driven processor for peel-apart instant films.